Apparatus for the introduction and manipulation of multiple telescoping catheters

ABSTRACT

A delivery apparatus includes a steerable guide sheath. The steerable guide sheath has a steerable portion, a pull ring located in the distal portion, and a pull wire coupled at one end to the pull ring and coupled at the opposite end to a control handle. The pull wire extends longitudinally through a pull-wire conduit. The steerable guide sheath further includes a compression-resistance portion made of metal and located in the distal portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/870,790, filed on May 8, 2020, which is a continuation of U.S. patentapplication Ser. No. 15/796,436, filed Oct. 27, 2017, now U.S. Pat. No.10,653,862, which claims the benefit of U.S. Provisional PatentApplication No. 62/418,528, filed Nov. 7, 2016, which are incorporatedherein by reference in their entireties for all purposes.

FIELD

The present application pertains to embodiments of steerableendovascular delivery devices.

BACKGROUND

Endovascular delivery devices are used in various procedures to deliverprosthetic medical devices or instruments to locations inside the bodythat are not readily accessible by surgery or where access withoutsurgery is desirable. Access to a target location inside the body can beachieved by inserting and guiding the delivery device through a pathwayor lumen in the body, including, but not limited to, a blood vessel, anesophagus, a trachea, any portion of the gastrointestinal tract, alymphatic vessel, to name a few. In one specific example, a prostheticheart valve can be mounted in a crimped state on the distal end of adelivery device and advanced through the patient's vasculature (e.g.,through a femoral artery) until the prosthetic valve reaches theimplantation site in the heart. The prosthetic valve is then expanded toits functional size such as by inflating a balloon on which theprosthetic valve is mounted, or by deploying the prosthetic valve from asheath of the delivery device so that the prosthetic valve canself-expand to its functional size.

The usefulness of delivery devices is largely limited by the ability ofthe device to successfully navigate through small vessels and aroundtight bends in the vasculature, such as through the inferior vena cavaor around the aortic arch. Various techniques have been employed toadjust the curvature of a section of a delivery device to help “steer”the valve through bends in the vasculature. Typically, a delivery deviceemploys a pull wire having a distal end fixedly secured to the steerablesection and a proximal end operatively connected to an adjustment knoblocated on a handle of the delivery device outside the body. The pullwire is typically disposed in a pull-wire lumen that extendslongitudinally in or adjacent to a wall of the delivery device, forexample, a sheath or catheter. Adjusting the adjustment knob, forexample, rotating the knob, applies a pulling force on the pull wire,which in turn causes the steerable section to bend.

A drawback of many guide sheaths is that they are prone to undesirabledeformation when deflected or flexed. For example, a guide sheathsubject to significant curvature, such as when accessing the mitralvalve in a transseptal approach, may kink at one or more locations alongthe radius of curvature, dramatically reducing the inner diameter of theguide sheath and resulting in unpredictable movement of the distal endof the guide sheath. A flexed guide sheath may also “pancake,” in whichthe cross-section of the catheter is ovalized due to a lack of adherencebetween the materials of adjacent layers of the sheath. Additionally, aflexed guide sheath may be reduced in length, or foreshortened, due toaxial compression of the shaft as it is flexed. Such deformation of theguide sheath, especially at the distal end, can interfere with theprecise positioning of an implant at the treatment site. Thus, a needexists for improved steerable shaft devices.

SUMMARY

Certain embodiments of the disclosure concern delivery apparatuses withsteerable shafts. In a representative embodiment, a delivery apparatuscomprises a steerable shaft having a proximal portion, a distal portion,and a pull-wire conduit that extends at least partially through theproximal and distal portions of the shaft. The delivery apparatusfurther includes a pull wire extending through the pull-wire conduit andhaving a proximal end portion and a distal end portion. The distal endportion of the pull wire is fixed to the distal portion of the shaft.The delivery apparatus further comprises an adjustment mechanismoperatively connected to the proximal end portion of the pull wire andconfigured to increase and decrease tension in the pull wire to adjustthe curvature of the distal portion of the shaft. The distal portion ofthe shaft comprises a steerable portion having one or more layers. Thesteerable portion includes a compression-resistance portion incorporatedinto a respective layer of the steerable portion, and extendingangularly along a portion of a cross-section of the layer. The layer ofthe steerable portion into which the compression-resistance portion isincorporated has a first hardness, and the compression-resistanceportion has a second hardness that is greater than the first hardness.

In another representative embodiment, a method comprises inserting ashaft of a delivery apparatus into the body of a patient, the shafthaving a proximal portion, a distal portion, and a pull-wire conduitthat extends at least partially through the proximal and distalportions. A pull wire extends through the pull-wire conduit, and thedistal portion of the shaft comprises a steerable portion having one ormore layers. The steerable portion includes a compression-resistanceportion incorporated into a respective layer of the steerable portionand extending angularly along a portion of a cross-section of the layer.The layer of the steerable portion into which the compression-resistanceportion is incorporated has a first hardness, and thecompression-resistance portion has a second hardness that is greaterthan the first hardness. The method further comprises applying tensionto the pull wire to adjust the curvature of the distal portion of theshaft.

In another representative embodiment, a delivery apparatus comprises asteerable shaft having a proximal portion, a distal portion, and apull-wire conduit that extends at least partially through the proximaland distal portions of the shaft. The delivery apparatus furtherincludes a pull wire extending through the pull-wire conduit and havinga proximal end portion and a distal end portion. The distal end portionof the pull wire is fixed to the distal portion of the shaft. Thedelivery apparatus further comprises an adjustment mechanism operativelyconnected to the proximal end portion of the pull wire and configured toincrease and decrease tension in the pull wire to adjust the curvatureof the distal portion of the shaft. The distal portion of the shaftcomprises one or more layers and a compression-resistance portionincorporated into a respective layer of the distal portion. Thecompression-resistance portion extends angularly along a portion of across-section of the layer and has a hardness that is greater than ahardness of the layer into which the compression-resistance portion isincorporated. The compression-resistance portion is angularly offsetfrom the pull-wire conduit along the cross-section of the layer.

The foregoing and other objects, features, and advantages of thedisclosed technology will become more apparent from the followingdetailed description, which proceeds with reference to the accompanyingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a representative embodiment of adelivery apparatus.

FIG. 2 is a side elevation view of the guide sheath of the deliveryapparatus of FIG. 1 .

FIG. 3 is cross-sectional side elevation view of the distal portion ofthe guide sheath of FIG. 1 illustrating the atraumatic tip portion andthe coupling portion.

FIG. 4 is a cross-sectional view of the guide sheath of FIG. 1 takenalong line 4-4 of FIG. 2 .

FIG. 5 is a side elevation view illustrating the pull ring and thedistal portions of the pull wires coupled to the pull ring.

FIG. 6 is a plan view of the distal portion of the guide sheath of FIG.1 illustrating the various layers of the guide sheath.

FIG. 7 is a perspective view of the distal portion of the guide sheathof FIG. 1 illustrating the compression-resistance portion of the outerlayer.

FIG. 8 is a cross-sectional view of the guide sheath of FIG. 1 takenalong line 8-8 of FIG. 2 .

FIG. 9 is a detail view of the pull-wire conduit receiving portion ofthe guide sheath of FIG. 8 .

FIG. 10 is a cross-sectional view of the guide sheath of FIG. 1 takenalong line 10-10 of FIG. 2 .

FIG. 11 is a perspective view of the guide sheath of FIG. 1 illustratingflexing of the guide sheath.

FIG. 12 is a cross-sectional view of an alternative embodiment of aguide sheath including one pull wire.

DETAILED DESCRIPTION

In particular embodiments, a delivery apparatus that can be used todeliver a medical device, tools, agents, or other therapy to a locationwithin the body of a subject can include one or more steerable cathetersor sheaths. Examples of procedures in which steerable catheters andsheaths are useful include neurological, urological, gynecological,fertility (e.g., in vitro fertilization, artificial insemination),laparoscopic, arthroscopic, transesophageal, transvaginal, transvesical,transrectal, and procedures including access in any body duct or cavity.Particular examples include placing implants, including stents, grafts,embolic coils, and the like; positioning imaging devices or componentsthereof, including ultrasound transducers; and positioning energysources, for example, for performing lithotripsy, RF sources, ultrasoundemitters, electromagnetic sources, laser sources, thermal sources, andthe like.

In some embodiments, the delivery apparatus includes a steerable shaftsuch as a guide sheath having one or more delivery catheters coaxiallydisposed within the guide sheath. In certain configurations, thedelivery catheters can comprise one or more balloons at or near a distalend portion of the catheter. In some implementations, the deliveryapparatus can be used to deliver a medical device through thevasculature, such as to a heart of the subject. These devices maycomprise one or more eccentrically positioned pull wires configured tocause the steerable shaft to curve in a given direction, or tostraighten. The steerable shaft can further comprise a steerable portionlocated near the distal end of the shaft including acompression-resistance portion that reduces foreshortening of the shaftand increases the degree of curvature attainable for a given pullingforce applied to the shaft by the pull wires, thereby enhancing thesteerability of the delivery apparatus.

FIG. 1 illustrates a representative embodiment of a delivery apparatus100 including a handle portion 102 and a shaft configured as a steerableguide sheath 104. The delivery apparatus 100 can be used to perform anydiagnostic, therapeutic, or interventional procedure where access to atarget location inside the body of a patient is desired. For example,the delivery apparatus 100 can be used to deliver and deploy aprosthetic device in the body, to deliver tools to a target location inthe body, or to deliver or introduce drugs or other agents, to name afew exemplary uses.

In certain embodiments, the delivery apparatus can include one or morecatheters coaxially disposed within and movable relative to the guidesheath 104. For example, in the illustrated configuration, the deliveryapparatus includes an intermediate catheter configured as a steerablecatheter 106 disposed within the guide sheath 104, and an inner catheterconfigured as a delivery or implant catheter 108 coaxially disposedwithin the steerable catheter 106. The implant catheter 108 can have aprosthetic device 110 mounted on a distal end of the implant catheter ina radially compressed state. In the illustrated configuration, theprosthetic device 110 is a prosthetic heart valve mounted on aninflatable balloon 112 at the distal end of the implant catheter, andthe delivery apparatus can be configured to deliver the prosthetic heartvalve 110 to one of the native valves of the heart (the aortic, mitral,pulmonary, or tricuspid valves).

In one specific example, the prosthetic heart valve 110 can be aplastically-expandable prosthetic heart valve, and the inflatableballoon 112 can be configured to expand and deploy the valve 110 at atreatment site. Exemplary configurations of the balloon 112 and implantcatheter 108 are further disclosed in U.S. Patent ApplicationPublication Nos. 2013/0030519, 2009/0281619, 2008/0065011, and2007/0005131, the disclosures of which are incorporated herein byreference in their entireties. Exemplary plastically-expandableprosthetic heart valves are disclosed in U.S. Patent ApplicationPublication Nos. 2010/0036484 and 2012/0123529, which are incorporatedherein by reference.

In another example, the delivery apparatus 100 can be used to deliverand deploy a self-expandable prosthetic heart valve (e.g., a prostheticvalve having a frame formed from a shape-memory material, such asnitinol). To deliver a self-expandable prosthetic valve, the prostheticvalve can be loaded into a delivery sheath or sleeve in a radiallycompressed state and advanced from the distal open end of the sheath atthe target location to allow the prosthetic valve to expand to itsfunctional size. The delivery sheath can be the distal end portion ofthe implant catheter 108, or the distal end portion of another shaftthat extends through the guide sheath 104. Further details regarding aself-expandable prosthetic valve and delivery devices for aself-expandable prosthetic valve are disclosed in U.S. PatentApplication Publication Nos. 2010/0049313 and 2012/0239142, which areincorporated herein by reference. Additionally, it should be understoodthat the delivery apparatus 100 can be used to deliver any of variousother implantable devices, such as docking devices, leaflet clips, etc.

Referring to FIGS. 1 and 2 , the steerable guide sheath 104 can includea proximal portion 114 coupled to the handle portion 102, and a distalportion 116. The distal portion 116 can include low durometer atraumatictip portion 118 coupled to a coupling portion 120 positioned proximallyof the atraumatic tip 118. In certain configurations, the atraumatic tip118 can be radiopaque. The distal portion 114 of the guide sheath 104can include a steerable portion 122 located proximally of the couplingportion 120 and configured to flex and unflex to adjust the curvature ofthe distal portion of the guide sheath, as described in detail below.

FIGS. 3-10 illustrate the construction of the guide sheath 104, andparticularly of the distal portion 116, in greater detail. The curvatureof the guide sheath 104 can be controlled by one or moreeccentrically-positioned pull wires (see, e.g., FIGS. 3, 5, and 8 ). Forexample, in the illustrated configuration the guide sheath 104 includestwo pull wires 124, 126 extending longitudinally through respectivepull-wire lumens or conduits 128, 130. The assembled pull wires 124, 126and conduits 128, 130 can be disposed in a pull-wire conduit portion 154of the guide sheath. In the illustrated configuration, the pull-wireconduit portion 154 is at least partially defined by a recess 142 of aninner layer 134 of the guide sheath. In the illustrated configuration,the recess 142 can extend into an inner diameter D₁ of the guide sheath104, although other configurations are possible. In certain embodiments,the pull-wire conduits 128, 130 can be made from a lubricious material,such as polytetrafluoroethylene (PTFE) to reduce friction between thepull wires 124, 126 and the respective conduits 128, 130 as the pullwires move within the conduits.

The pull wires 124, 126 can be coupled at one end to a pull ring 144embedded in the coupling portion 120, and coupled at the opposite end toa control mechanism configured as a rotatable knob 132 of the handle 102(see FIG. 1 ). Rotation of the knob 132 can increase and decreasetension in the pull wires 124, 126 which, in turn, can cause the distalportion 116, and particularly the steerable portion 122, to flex andunflex to control the curvature of the guide sheath. A cross-sectionalview of the coupling portion 122 illustrating the pull ring 144encapsulated in the coupling portion is shown in FIG. 4 .

The pull ring 144 and the distal portions of the pull wires 124, 126 areshown in isolation in FIG. 5 . In the illustrated configuration, thepull ring 144 can define a plurality of openings 156 about itscircumference. During fabrication of the guide sheath 104, the polymericmaterial of the coupling portion 120 can be reflowed over the pull ring144, and the material can flow through the openings 156 to encapsulatethe pull ring in the coupling portion, as shown in FIG. 3 .Additionally, although the illustrated embodiment includes two pullwires 124, 126, it should be understood that other configurations arepossible. For example, the guide sheath 104 can include any suitablenumber of pull wires having any suitable size or layout, including asingle pull wire (see FIG. 12 ), or more than two pull wires, dependingupon the requirements of the device. The particular embodimentillustrated herein includes two pull wires because, in someconfigurations, two pull wires can occupy a smaller cross-sectional areathan that of a single larger pull wire for transmitting a given force tothe pull ring 144, particularly when relatively large forces arerequired (such as when flexing the guide sheath loaded with thesteerable catheter 106 and the implant catheter 108).

Referring to FIGS. 3-10 , the guide sheath 104 can include a pluralityof layers comprising a variety of different materials at differentlocations along the length of the guide sheath and configured to impartvarious properties to the guide sheath. For example, with reference toFIGS. 3 and 6 , the steerable portion 122 of the guide sheath 104comprises a first inner layer 134 defining an inner diameter D₁ of theguide sheath 104, and a second pull-wire conduit encapsulating layer 135disposed radially outward of the inner layer 134. A third helicallycoiled layer 136 extends over the pull-wire conduit encapsulating layer135. A fourth braided layer 138 is disposed over the helically coiledlayer 136, and a fifth outer layer 140 is disposed over the braidedlayer, and defines an outer diameter D2 of the guide sheath. FIG. 6illustrates a plan view of the distal portion 116 of the guide sheath104 with each of the outer layer 140, the braided layer 138, thehelically coiled layer 136, and the pull-wire conduit encapsulatinglayer 135 shown partially removed to illustrate the construction of theguide sheath.

The first layer 134 extends along the full length of the guide sheath104, and can be made from (or coated with) a lubricious material (e.g.,PTFE) to allow the steerable intermediate catheter 106 to slide relativeto the guide sheath 104 within the guide sheath's lumen. As statedabove, the first layer 134 can also define the recess 142 of thepull-wire conduit portion 154 in which the pull wires 124, 126 andconduits 128, 130 are received.

The pull-wire conduit encapsulating layer 135 can be disposed betweenthe first inner layer 134 and the helically coiled layer 136, and canhave a thickness that varies angularly around the circumference of theguide sheath. For example, with reference to FIGS. 8 and 9 , the portionof the pull-wire conduit encapsulating layer 135 proximate the pull-wireconduit portion 154 can be sufficiently thick such that the layer 135encapsulates the pull-wire conduits 128, 130 in the pull-wire conduitportion. Meanwhile, the portion of the pull-wire conduit encapsulatinglayer 135 opposite the pull-wire conduit portion 154 can be relativelythin. Alternatively, the pull-wire conduit encapsulating layer 135 canextend around only a portion of the cross-section of the guide sheath,such as around the portion (e.g., half) including the pull-wire conduits128, 130. In such a configuration, the helically coiled layer 136 candirectly contact the inner layer 134 along the portion of the innerlayer's cross-section that is opposite the pull-wire conduits, and cantransition over the pull-wire conduit encapsulating layer 135 at thelocation along the circumference of the inner layer 134 where thepull-wire conduit encapsulating layer originates. In some embodiments,the pull-wire conduit encapsulating layer 135 can be made from anysuitable polymer, such as any of various polyether block amides (e.g.,Pebax®). In certain configurations, the pull-wire conduit encapsulatinglayer 135 can extend from the proximal end of the coupling portion 120,through the steerable portion 122, to the pull wire exit 148 (FIG. 2 ).

The helically coiled layer 136 can be formed from, for example, a wirehelically wrapped or wound about the pull-wire conduit encapsulatinglayer 135 or the first layer 134. In the illustrated embodiment, thehelically coiled layer 136 can extend from adjacent the pull ring 144proximally through the coupling portion 120 and the steerable portion122 to a transition region 146 (FIG. 1 ) located between the proximaland distal portions 114, 116. In certain embodiments, the transitionregion 146 where the helically coiled layer 136 ends can be the locationat which the outer layer 140 changes from a material having a relativelyhigher durometer or hardness (e.g., 63D Pebax®) to a material having arelatively lower durometer (e.g., a polyamide such as VESTAMID®). Insome embodiments, gradually varying (e.g., stepwise) the hardness of theouter layer 140 or the other layers of the shaft along their length canreduce the likelihood of kinking, fracture, or warping of the shaftduring flexing, or when traversing vessels of the body. Additionally, incertain examples, the helically coiled layer 136 can be made fromstainless steel or titanium flat wire wound at, for example, 50 coilsper inch with a pitch of 0.020 inch, and can be configured to resistkinking or crushing of the guide shaft 104, and particularly of thesteerable portion 122, when it is flexed.

The braided layer 138 can extend over the helically coiled layer 136. Inthe illustrated configuration, the braided layer 138 can extend from thecoupling portion 120 proximate the pull ring 144 proximally to, forexample, the pull wire exit 148. The braided layer 138 can be, forexample, metal wires braided together in a pattern to form a tubularlayer over the helically coiled layer 136. For example, in theillustrated embodiment the braided layer 138 is made from stainlesssteel or titanium flat wires braided in an over 1 under 1 pattern,although any suitable braid pattern can be used. For example, in anotherrepresentative embodiment, the wires of the braided layer 138 can bebraided in a 1 over 2, under 2 pattern with a pick count of 60 picks perinch (PPI). The braided layer 138 can be configured to, for example,resist undesirable torsional deformation of the guide sheath 104 toallow the guide sheath to transmit torque, which can aid in positioningthe implant at the treatment site. The braided layer 138 can alsoprovide crush or kink-resistance properties to the guide sheath 104. Inthe illustrated configuration, the coupling portion 120 can also includea braided layer 158 disposed beneath the pull ring 144, as shown inFIGS. 3 and 4 .

The outer layer 140 can comprise, for example, any of a variety ofpolymeric materials such as polyamides (e.g., VESTAMID®), polyetherblock amides (e.g., Pebax®), nylon, or any other suitable biocompatiblepolymer or combinations thereof along its length. In the illustratedconfiguration, the pull-wire conduit encapsulating layer 135, thehelically coiled layer 136, and the braided layer 138 can terminatedistally of the proximal end of the guide sheath 104. For example, insome configurations these layers can terminate at the pull wire exit148. Proximally of the pull wire exit 148, the outer layer 140 canincrease in thickness to maintain a substantially uniform outer diameteralong the length of the guide sheath, as illustrated in FIG. 10 .

Referring to FIGS. 7 and 8 , the distal portion 116 of the guide sheath104 can include a compression-resistance portion 150. In the illustratedconfiguration, the compression-resistance portion 150 is incorporatedinto the outer layer 140, and forms a respective part of the steerablesection 122. As illustrated in FIG. 7 , the compression-resistanceportion 150 can extend along a length L of the steerable portion 122.The compression-resistance portion 150 can also extend circumferentiallyor angularly along, or occupy a respective portion of, the cross-sectionof the outer layer 140. For example, with reference to FIG. 8 , theangular extent of the compression-resistance portion 150 along thecross-section of the outer layer 140 is denoted by the angle θ. In someembodiments, the angle θ can be from 10 degrees to 180 degrees (or halfof the circumference of the cross-section). In some embodiments, theangle θ can be from 10 degrees to 90 degrees. In the embodiment of FIG.8 , the angle θ is 60 degrees.

In certain configurations, the compression-resistance portion 150 can bedisposed opposite the pull wire conduits 128, 130. For example, in theillustrated configuration, the compression-resistance portion 150 isangularly offset from the pull wire conduit portion 154 by 180 degreessuch that it is located diametrically opposite the pull wire conduits128, 130. In this configuration, a plane 152 that bisects the pull wireconduit portion 154 also bisects the compression-resistance portion 150,as shown in FIG. 8 . In the configuration of FIG. 8 including two pullwires and conduits, the plane 152 bisecting the pull-wire conduitportion 154 passes between the respective conduits 128, 130. However, inconfigurations including a single pull wire, such as the alternativeconfiguration illustrated in FIG. 12 , a single pull wire 160 andconduit 162 can be coaxially aligned with the pull-wire conduit portion154 such that the plane 152 bisecting the pull-wire conduit portion 154and the compression-resistance portion 150 also bisects the pull wire160 and the conduit 162. In other configurations, thecompression-resistance portion 150 can be angularly offset from thepull-wire conduit portion 154 along the cross-section of the outer layer140 by, for example, from 90 degrees to 180 degrees, as desired.

The compression-resistance portion 150 can be made from a materialhaving a relatively higher hardness or durometer than the remainder ofthe outer layer 140 in the steerable portion 122 in which thecompression-resistance portion is incorporated. For example, in certainembodiments the compression-resistance portion 150 can have a durometerthat is from 1.5 times to 5 times greater than a durometer of theremainder of the outer layer 140 in the steerable portion 122. In someembodiments, the durometer of the compression-resistance portion 150 canbe from 2 times to 3 times greater than the durometer of the remainderof the outer layer 140 in the steerable portion 122. In an exemplaryembodiment, the compression-resistance portion 150 can be made fromPEBAX® having a durometer of 72D, and the remainder of the outer layer140 of the steerable portion 122 can be made from PEBAX® having adurometer of 25D, such that a ratio of the durometer of thecompression-resistance portion 150 and the durometer of the remainder ofthe outer layer 140 in the steerable portion 122 is 2.9:1. In someembodiments, the ratio of the durometer of the compression-resistanceportion 150 to the durometer of the remainder of the outer layer 140 inthe steerable portion 122 can be 3:1.

In other embodiments, the compression-resistance portion 150 can be madeof any of various materials exhibiting suitable hardness properties,including metals such as stainless steel, titanium, nickel titaniumalloys such as nitinol, cobalt chromium, or other polymers. In addition,in certain configurations, the compression-resistance portion need nothave a thickness equal to the overall thickness of the outer layer 140.For example, the compression-resistance portion 150 can have a thicknessthat is less than the overall thickness of the outer layer, and may beencapsulated within the outer layer, as desired. The durometer of thecompression-resistance portion 150 can also vary along its length. Forexample, the proximal portion of the compression-resistance portion 150can have a relatively lower durometer than the distal portion, or viceversa.

The compression-resistance portion 150 can provide a variety ofadvantageous characteristics to the steerable portion 122 of the guidesheath 104. For example, the relatively higher durometer of thecompression-resistance portion 150 can provide axial strength to thesteerable portion 122. This can significantly reduce or preventundesirable foreshortening of the guide sheath 104, and particularly ofthe steerable portion 122, when the guide catheter is flexed. Moreparticularly, the compression-resistance portion 150 can reduce axialcompression of the guide sheath and associated wrinkling of the materialwhen the guide sheath is flexed compared to when it is in anon-deflected state. Such axial compression and wrinkling of thematerial can decrease the length of the guide sheath 104 as the materialis deformed, and can damage the guide sheath. By reducing or eliminatingforeshortening of the guide sheath 104 when it is flexed, thecompression-resistance portion 150 can reduce the need for the operatorto longitudinally reposition the delivery apparatus (e.g., by advancingor retracting the delivery apparatus through the patient's vasculature)in order to obtain or regain a desired position of the implant at thetreatment site after flexing the guide sheath.

Additionally, the location of the compression-resistance portion 150angularly offset from the pull wire conduits 128, 130 can aid ininitiating deformation of the steerable portion 122 of the guide sheathin a specified direction. For example, when the compression-resistanceportion 150 is located opposite the pull wire conduits 128, 130, theaxial stiffness of the compression-resistance portion can inducedeflection of the steerable portion 122 in a direction away from thecompression-resistance portion when the guide sheath is flexed, asillustrated in FIG. 11 . The compression-resistance portion 150 can alsoreduce or prevent ovalizing (also referred to as “pancaking”) of theguide sheath by reducing longitudinal movement of the different layersof the sheath relative to one another when the sheath is flexed,especially in cases in which one or more constituent layers (e.g., PTFElayers such as inner layer 134) are not strongly adhered to thesurrounding layer(s).

The compression-resistance portion 150 can also increase the degree offlexion of the distal portion 116 attainable for a given force appliedto the distal portion by the pull wires 124, 126, without damaging theguide sheath. The angle of flexion of the distal portion 116 is denoteda, and is illustrated in FIG. 11 . For example, by reducingforeshortening of the guide sheath 104, a greater proportion of theforce applied by the pull wires 124, 126 is available to flex the guidesheath instead of elastically compressing the guide sheath.Additionally, the compression-resistance portion 150 can reduce orprevent slackening of the pull wires 124, 126 attendant toforeshortening of the guide sheath 104 when it is flexed, resulting in agreater degree of curvature attainable for a given pull wire travel ascompared to typical guide sheaths. As used herein, the term “pull wiretravel” refers to the linear distance that a given point along thelength of a pull wire moves with respect to a stationary reference(e.g., a pull wire conduit) when tension is applied to the pull wire.

Additionally, the compression-resistance portion 150, together with thehelically coiled layer 136, and the braided layer 138 described above,can provide significant synergistic advantages that improve theperformance of the guide sheath 104 over known steerable sheaths andcatheters. For example, the distal portion of an unloaded guide sheath(e.g., a guide sheath without a delivery catheter or other shaftextending through its lumen) having an inner diameter of 22 Fr andincluding the compression-resistance portion, helically coiled layer,and braided layer features is capable of flexing nearly 355 degreeswithout kinking, and without significant foreshortening, under a forceof 175 N applied by the pull wires. In this example, 50 mm of pull wiretravel were required to apply a force of 175 N to the distal portion ofthe guide sheath. In contrast, for a typical steerable catheter devicewithout the compression-resistance portion and without a deliverycatheter or other sheath extending through its lumen, a force of 175 Nproduces 270 degrees of flexure and requires 60 mm of pull wire travel,and the guide sheath can be expected to foreshorten by 6 mm to 10 mm.

In another example, the distal portion of a guide sheath having an innerdiameter of 22 Fr and including the above compression-resistanceportion, helically coiled layer, and braided layer features, and loadedwith a delivery catheter and an implant catheter extending coaxiallywithin the lumen of the guide sheath, was capable of flexing 270 degreeswithout kinking, and without significant foreshortening, under a forceof 250 N applied by the pull wires. In this example, 40 mm of pull wiretravel were required to apply a force of 250 N to the distal portion ofthe guide sheath. In contrast, for a steerable catheter device withoutthe compression-resistance portion and loaded with a delivery catheterand an implant catheter, a force of 250 N produces 180 degrees offlexure and requires 70 mm of pull wire travel, and the guide sheath canbe expected to foreshorten by 6 mm to 10 mm.

In use, the delivery apparatus 100 can be introduced and advancedthrough the patient's vasculature using any known delivery technique. Ina transfemoral procedure, the delivery apparatus can be inserted througha femoral artery and the aorta to access the heart (typically, but notexclusively used for aortic valve replacement). In a transeptalprocedure (typically used for aortic or mitral valve replacement), thedelivery device can be advanced to the right atrium, such as via afemoral vein, and through the septum separating the right and leftventricles. The disclosed embodiments can be particularly useful fordelivering a prosthetic valve to the native mitral valve, as thetorquability of the guide sheath 104 and the relatively high degree ofcurvature achievable with the distal portion 116 allows for precisepositioning of the prosthetic valve at the target site despite thetortuous pathway the delivery apparatus must follow to access the mitralvalve in some approaches. In a transventricular procedure, the deliveryapparatus can be inserted through a surgical incision made on the barespot on the lower anterior ventricle wall (typically, but notexclusively used for aortic or mitral valve replacement). In atransatrial procedure, the delivery apparatus can be inserted through asurgical incision made in the wall of the left or right atrium. In atransaortic procedure, the delivery apparatus can be inserted through asurgical incision made in the ascending aorta and advanced toward theheart (typically, but not exclusively used for aortic valvereplacement).

In certain of these procedures, the combination of thecompression-resistance portion 150, the helically coiled layer 136, andthe braided layer 138 can aid in precisely positioning a prostheticdevice, such as the heart valve 110, at a treatment site. For example,in a transseptal procedure to access the mitral valve, after the distalend of the delivery apparatus is advanced to the treatment site, thedistal portion 116 of the guide sheath 104 can be flexed to axiallyalign the prosthetic valve 110 with the mitral valve (e.g., 180 degreesor more, in certain examples). While the distal portion 116 is in aflexed state, the guide sheath 104 can also be torqued to radiallyposition the prosthetic valve 110 with respect to the mitral valve. Thecombination of the compression-resistance portion 150, the helicallycoiled layer 136, and the braided layer 138 can allow the guide sheathto flex without significant foreshortening or kinking, and to be torquedwithout undesirable torsional deformation of the shaft or associatedunpredictable rotational motion of the guide sheath.

It should be understood that in alternative configurations, thecomponents of the disclosed delivery apparatus embodiments can berearranged without departing from the spirit of the disclosure. Forexample, the locations of the helically coiled layer 136 and the braidedlayer 138 can be reversed such that the helically coiled layer is on topof the braided layer. Alternatively, the helically coiled layer 136 andthe braided layer 138 can be separated from one another by one or moreintermediate layers. Additionally, the compression-resistance portion150 need not be a respective portion of the outer layer 140, but can beincorporated into any suitable layer in the guide sheath 104. Thecompression-resistance portion 150 also need not extend along the entirelength of the steerable portion 122, but can extend along any suitableportion of the steerable portion. The disclosed compression-resistanceportion, helically coiled layer, and braided layer features describedherein can also be applicable to other types of steerable catheterdevices, such as delivery catheters.

GENERAL CONSIDERATIONS

For purposes of this description, certain aspects, advantages, and novelfeatures of the embodiments of this disclosure are described herein. Thedisclosed methods, apparatus, and systems should not be construed asbeing limiting in any way. Instead, the present disclosure is directedtoward all novel and nonobvious features and aspects of the variousdisclosed embodiments, alone and in various combinations andsub-combinations with one another. The methods, apparatus, and systemsare not limited to any specific aspect or feature or combinationthereof, nor do the disclosed embodiments require that any one or morespecific advantages be present or problems be solved.

Although the operations of some of the disclosed embodiments aredescribed in a particular, sequential order for convenient presentation,it should be understood that this manner of description encompassesrearrangement, unless a particular ordering is required by specificlanguage set forth below. For example, operations described sequentiallymay in some cases be rearranged or performed concurrently. Moreover, forthe sake of simplicity, the attached figures may not show the variousways in which the disclosed methods can be used in conjunction withother methods. Additionally, the description sometimes uses terms like“provide” or “achieve” to describe the disclosed methods. These termsare high-level abstractions of the actual operations that are performed.The actual operations that correspond to these terms may vary dependingon the particular implementation and are readily discernible by one ofordinary skill in the art.

As used in this application and in the claims, the singular forms “a,”“an,” and “the” include the plural forms unless the context clearlydictates otherwise. Additionally, the term “includes” means “comprises.”Further, the terms “coupled” and “associated” generally meanelectrically, electromagnetically, or physically (e.g., mechanically orchemically) coupled or linked and does not exclude the presence ofintermediate elements between the coupled or associated items absentspecific contrary language.

In the context of the present application, the terms “lower” and “upper”are used interchangeably with the terms “inflow” and “outflow”,respectively. Thus, for example, the lower end of the valve is itsinflow end and the upper end of the valve is its outflow end.

As used herein, the term “proximal” refers to a position, direction, orportion of a device that is closer to the user and further away from theimplantation site. As used herein, the term “distal” refers to aposition, direction, or portion of a device that is further away fromthe user and closer to the implantation site. Thus, for example,proximal motion of a device is motion of the device toward the user,while distal motion of the device is motion of the device away from theuser. The terms “longitudinal” and “axial” refer to an axis extending inthe proximal and distal directions, unless otherwise expressly defined.

Unless otherwise indicated, all numbers expressing quantities ofcomponents, distances, forces, ratios, angles, percentages, and soforth, as used in the specification or claims are to be understood asbeing modified by the term “about.” Accordingly, unless otherwiseindicated, implicitly or explicitly, the numerical parameters set forthare approximations that can depend on the desired properties soughtand/or limits of detection under test conditions/methods familiar tothose of ordinary skill in the art. When directly and explicitlydistinguishing embodiments from discussed prior art, the embodimentnumbers are not approximates unless the word “about” is recited.Furthermore, not all alternatives recited herein are equivalents.

In view of the many possible embodiments to which the principles of thedisclosed technology may be applied, it should be recognized that theillustrated embodiments are only preferred examples and should not betaken as limiting the scope of the disclosure. Rather, the scope of thedisclosure is at least as broad as the following claims.

What is claimed is:
 1. A steerable guide sheath, comprising: a steerableportion configured to flex and unflex to adjust the curvature of adistal portion of the guide sheath; a pull ring located in the distalportion; a first pull wire coupled at one end to the pull ring andcoupled at the opposite end to a control handle, wherein the first pullwire extends longitudinally through a first pull-wire conduit; and acompression-resistance portion made of metal and located in the distalportion.
 2. The steerable guide sheath of claim 1, wherein the metal isstainless steel, titanium, nickel titanium alloy, or cobalt chromium. 3.The steerable guide sheath of claim 1, further comprising an adjustmentknob located on the handle, wherein rotating the adjustment knob appliesa pulling force on the first pull wire to cause the steerable portion tobend.
 4. The steerable guide sheath of claim 1, wherein the compressionresistance portion is disposed opposite the first pull wire conduit. 5.The steerable guide sheath of claim 1, wherein the compressionresistance portion has a thickness less than the distal portion.
 6. Thesteerable guide sheath of claim 1, further comprising a second pull wirecoupled at one end to the pull ring and coupled at the opposite end tothe control handle, wherein the second pull wire extends longitudinallythrough a second pull-wire conduit
 7. The steerable guide sheath ofclaim 6, wherein a plane bisecting the distal portion and passingbetween the first and second pull-wire conduit bisects thecompression-resistance portion.
 8. The steerable guide sheath of claim1, further comprising an atraumatic tip portion located distally of thesteerable portion.
 9. A delivery apparatus for a prosthetic device,comprising: a steerable guide sheath; a steerable catheter disposedwithin the guide sheath; an implant catheter coaxially disposed withinthe steerable catheter, wherein the prosthetic device is mounted on adistal end of the implant catheter; wherein the steerable guide sheathcomprises: a steerable portion configured to flex and unflex to adjustthe curvature of a distal portion of the guide sheath; a pull ringlocated in the distal portion; a first pull wire coupled at one end tothe pull ring and coupled at the opposite end to a control handle,wherein the first pull wire extends longitudinally through a firstpull-wire conduit; and a compression-resistance portion made of metaland located in the distal portion.
 10. The delivery apparatus of claim9, wherein the metal is stainless steel, titanium, nickel titaniumalloy, or cobalt chromium.
 11. The delivery apparatus of claim 9,further comprising an adjustment knob located on the handle, whereinrotating the adjustment knob applies a pulling force on the first pullwire to cause the steerable portion to bend.
 12. The delivery apparatusof claim 9, wherein the compression resistance portion is disposedopposite the first pull wire conduit.
 13. The delivery apparatus ofclaim 9, wherein the compression resistance portion has a thickness lessthan the distal portion.
 14. The delivery apparatus of claim 9, furthercomprising a second pull wire coupled at one end to the pull ring andcoupled at the opposite end to the control handle, wherein the secondpull wire extends longitudinally through a second pull-wire conduit 15.The delivery apparatus of claim 14, wherein a plane bisecting the distalportion and passing between the first and second pull-wire conduitbisects the compression-resistance portion.
 16. The delivery apparatusof claim 9, further comprising an atraumatic tip portion locateddistally of the steerable portion.
 17. A steerable guide sheath,comprising: a steerable portion configured to flex and unflex to adjustthe curvature of a distal portion of the guide sheath; a pull ringlocated in the distal portion; a first pull wire coupled at one end tothe pull ring and coupled at the opposite end to an adjustment knoblocated on a control handle, wherein the first pull wire extendslongitudinally through a first pull-wire conduit; a second pull wirecoupled at one end to the pull ring and coupled at the opposite end tothe adjustment knob, wherein the second pull wire extends longitudinallythrough a second pull-wire conduit; and a compression-resistance portionmade of metal and located in the distal portion opposite the first andsecond pull wire conduits, wherein a plane bisecting the distal portionand passing between the first and second pull-wire conduit bisects thecompression-resistance portion.
 18. The steerable guide sheath of claim17, wherein the metal is stainless steel, titanium, nickel titaniumalloy, or cobalt chromium.
 19. The steerable guide sheath of claim 17,wherein the compression resistance portion has a thickness less than thedistal portion.
 20. The steerable guide sheath of claim 17, furthercomprising an atraumatic tip portion located distally of the steerableportion.